Sirens wailed throughout Israel early Tuesday and the country's more than seven million residents were asked to enter shelters and "safe rooms", the peak of a major civil defence drill.

Sirens wailed throughout Israel early Tuesday and the country's more than seven million residents were asked to enter shelters and "safe rooms", the peak of a major civil defence drill.

The unusual, five-day exercise that began Sunday under the codename "Turning Point 3", prepared for a scenario where Israel is attacked by hundreds of long and short-range missiles from multiple fronts.

Prime Minister Benjamin Netanyahu has denied a link to Iran, which has vowed to respond if Israel were to attack its nuclear facilities.

But the unprecedented scope of the drill further inflamed already widespread speculation about possible Israeli preparations for a strike on Iran.

Leading Israeli experts on Iran nonetheless told DPA Tuesday they did not believe the drill was necessarily a harbinger of an attack to come against Iran. Rather, they said, it was part of the continuous implementation of lessons learned from the 2006 war between Israel and the radical Shia Hezbollah movement and Israel's more recent offensive in the Gaza Strip.

During those confrontations, Israel was battered by a combined total of more than 5,000 rockets, fired by Hezbollah from southern Lebanon and by Palestinian militants from Gaza.

The Israeli military's Home Front Command said it was pleased with the public's participation, with army officials describing the response as "good", both in schools and among the general public.

Israelis had been informed how to conduct themselves during the exercise via radio and television for days. They were told that if entering shelters or "protected rooms", set up in advance, were to cause "major disruption" to their day, this was not obligatory. In all other cases, however, they were advised to participate and remain in the protected area for 10 minutes.

They had been instructed to clear out shelters weeks in advance.

Several malfunctions were reported however. In some parts of the country, including Tel Aviv and Jerusalem, the two largest cities, sirens either did not sound or were muted. In others, some public shelters remained closed.

An awkward moment occurred in the Knesset, when the parliament building's director general, in charge of implementing the drill, did not know where to go when the sirens went off and tried to enter the locked plenum hall. All Knesset workers had been briefed beforehand, Israel Radio said, and there were signs throughout the building giving directions.

Netanyahu, who since taking office March 31 has made stopping Iran from obtaining nuclear weapons a top priority, told his cabinet Sunday the drill was "a routine action unrelated to any special event of one kind" or intelligence warnings.

He said it was necessary because Israel must ensure its capabilities develop "in parallel with that of our enemies".

Ephraim Asculai, a senior research fellow at Israel's Institute for National Security Studies, acknowledged that the drill was "unprecedented", but said it was held now because of "the knowledge that our neighbours and very distant neighbours now have weapons which can strike anywhere in Israel".

The missile threat "is here to stay," said Uzi Eilan, a former director of research and development at the Israeli defence ministry and now a senior fellow at the same Tel Aviv-based think-tank.

Professor Eldad Pardo, a Middle East expert at the Hebrew University of Jerusalem's Truman Institute, thought the drill prepared among others for a scenario in which Israel, even if it did not attack Iran alone, would be caught in the middle of an armed confrontation between Tehran and the West once diplomacy had exhausted itself.

In such a case, not only Iran, but also its allies in the region, including Syria, Hezbollah and the radical Islamist Hamas movement ruling Gaza, were all likely to retaliate by attacking Israel.